Thread cutting chaser



Nov. 23, 1937. A. F. BREITENSTEIN 2,099,721

THREAD CTTING GHASER Filed June l, 1936 IH llllll' IlIIIIIlI llllllll' Patented Nov. 23, 1937 UNITED STATES THREAD CUTTING CHASER Albert F. Breitenstein, New Haven, Conn., as-

signor to The Geometric Tool Company, New Haven, Conn., a corporation of Connecticut Application June 1, 1936, Serial No. 82,717

6 Claims.

, This invention relates to improvement in chasers for cutting threads on various objects, such for instance as upon rods, tubes, etc.

In mass-production thread-cutting practice it is customary to engage a plurality of chasers with the article to be threaded. This practice often, especially in producing coarse-pitch threads, causes the mutilation of the starting-portion of the thread formed by the front tooth of the particular chaser or chasers which first contact the Work with a full or nearly-full cutting-tooth before a full or nearly-full cutting-tooth of the succeeding or tracking chaser or chasers can Contact the article and stabilize the cutting action.

The main object of the present invention,

therefore, is to provide a thread-cutting chaser which will obviate the thread mutilation above referred to. o With the above and other objects in View, as will appear to those skilled in the art from the following, considered in conjunction with the accompanying drawing and appended claims, the present invention includes all features disclosed therein which are novel over the prior art.

In the accompanying drawing:

Fig. 1 is a face view of a die-head upon which are mounted four chasers, two of which embody the present invention;

Fig. 2 is a broken sectional View on an enlarged scale, taken on the line 2 2 of Fig. 1;

Fig. 3 is a face view of a circular chaser embodying the present invention;

Fig. 4 is an edge View thereof;

Fig. 5 is a face view of a toothed blank from which a chaser embodying the present invention may be formed;

' Fig. 6 is an edge view thereof;

Fig. '7 is a face View of the blank after the 40 same has been chamfered;

Fig. 8 is an edge view thereof;

Fig. 9 is a face View of the blank after the same has been provided With a checking-shoulder; and

Fig. 10 is an edge view thereof.

Prior to the detailed description of the improved chaser, attention is called to the showing in Fig. 1, in which a die-head of any approved construction carries four (more or less) radially-movable chaser-carriers 2 I, upon each of which is mounted a so-called circular chaser. The four chasers referred to are designated respectively as A, B, C, and D, and of Which the chasers A and C correspond to each other as do also the chasers B and D. The two chasers B and D referred to embody the present invention, while the chasers A and C are of usual form.

For purposes of description, it may be assumed that 'the chasers A, B, C, and D of the die-head 2U are designed and arranged to cut double 5 threads upon a 5%, rod. Let it further be assumed that the threads to be produced are of 1A, pitch and, therefore, have a 1A. lead owing to the thread being double.

Under these conditions, the chasers A and B l0 cooperate in producing one of the double threads and the chasers C and D similarly cooperate in producing the other of the double threads referred to.

Each of the chasers A, B, C, and D is formed 15.'

upon its periphery with a series of circumferen-` tially-extending thread-cutting teeth 22, each of which terminates in a cutting-lip 23 forming one end of a cut-away portion 24 of each of the otherwise cylindrical chasers. ment to one of the radially-movable chasercarriers 2l, each Chaser is formed with an axial passage 25 for the reception of suitable fasteningmeans.

Each of the chasers A, B, C, and D is formed with a chamfer 26 which facilitates the initial engagement of the chasers with the work 21 indicated in Fig. 2. It will be noted by reference to Fig. 2 in particular that the chamfer 26 of the Chaser D extends up onto the advance face of the 30 front tooth 22a thereof.

It is to be here noted that the descriptive matter relating to the chaser D applies with equal force to the chaser B, and similarly that the descriptive matter relating to the chaser C applies With equal force to the Chaser A.

The chaser C is the tracking Chaser, so to speak, of the chaser D and, therefore, has its cutting-teeth 22 located in line with the gaps between the cutting-teeth of the Chaser D and hence the formation of the chamfer 26 of the Chaser C results in leaving on the said chaser a very incomplete front tooth 22h.

The advance face of the front tooth 22a of each of the chasers B and D is cut away to provide a checking-shoulder 28 which intersects the chamfer 26, as clearly shown in Fig. 2. The important point about the checking-shoulder 28, just referred to, is that it is located from the back or trailing face of the tooth 22a a distance repre- 50 sented by the dimension E (Fig. 2) which is less than the dimfension F representing the normal root thickness of the cutting-teeth 22. For purposes of comparison, broken lines 22c have been applied to Fig. 2 adjacent the tooth 2 2a to 55 For its attach- 2b' "-back face of the particulartooth upon which it responding to the desired cross-sectional form of Vthe desired thread-cutting teeth 22. The blank may now be provided on its forward face with the chamfer 26 as shown in Figs. 7 and 8, after which the appropriate portion of the chamfer may be cut away to provide the checking-shoulv der 28 as shown in Figs. 9 and 10. The said checking-shoulder preferably has a slope corresponding to the slope of the advance face of the teeth 22. After the blank has reached the stage shown in Figs. 9 and 10, a portion of its periphery is cutaway as at 24 to provide the desired cutting-lip 23 as shown particularly well in Fig, 3.

By reference to Fig. 2, it will be seen that the checking-shoulder 28 Yof the chaser D contacts the work before the first substantially-full tooth 22d of the chaser C, which latter complements the chaser D inr cutting a given thread. The checking-shoulder 28 then serves to assist in stabilizing the cutting action of the group of chasers and minimizes the tendency of the teeth of one chaser to unduly advance or hold back with respect to the teeth of another chaser, so that the mutilation of the starting portion of the threads upon the Work 21 is avoided. y

In the above description and in the accompanying drawing only so-called circular chasers have been shown and described, but it will be obvious to those skilled in the art that the inven- .tion may be applied to other well-known types of chasers. Y

.4% From the foregoing, it will be seen that the front tooth of the chaser D, as well as the chaser Y thread-cutting teeth 22 of the said chaser. Many theories may be advanced as to the exact functioning of the checking-shoulder 28, but it is suf-V is formed, it serves to overcome the mutilation of the starting portion of threads formed upon rods and the like.

The invention may be carried out in other speciiic ways than those herein set forth without lency range of the appended claims are intended Yto be embraced therein.

I claim: Y 1. A thread-cutting chaser having a plurality of thread-cutting teeth, including a front threadcutting tooth, offsetting therefrom; the said front tooth having its advance face chamfered and also havinga 4further portionofits. advance face cut away to. provide a checking-shoulder lintersecting and extending at an angle to the chamfered portion of the tooth. Y

2. A thread-cutting chaser having a plurality of thread-cutting teeth, including a front threadcuttingrtooth, offsetting therefrom; the said front tooth hav-ingpits advance face chamfered and also having a further portion of its advance face cut away to provide a checking-shoulder extending substantially parallel with the advance Vface of the. other of said thread-cutting teeth.

3. A thread-cutting chaser having a plurality of thread-cutting teeth,including a front threadcutting tooth, offsetting therefrom; the said front tooth havingfits advance face chamferedand also having a -further' portion Vof* itsl advance face cut away to' provide achecking-shoulderk -located* fromthe trailing-face-of the said front toothV a.

of said-thread-cutting teeth.

4. A thread-cutting chaser having a plurality ofthread-cutting teeth, including a front threadc-utting tooth, offsetting therefrom, the said front tooth having its advance face chamfered and also havinga further portion of its advance face cut away-.to provide -a checking-shoulder extending substantially parallel with the advance face of the other of `said thread-cutting teeth and 1ocated'from the l'trailing-face of the said front tootha distance less thank the root-thickness of the other of said thread-cutting teeth.

5.'A-circular thread-cutting chaser having a plurality of peripherally-extending thread-cutting teeth offsetting therefrom, including'a front peripherally-extending thread-cutting tooth; the said front Vtooth having its advance'face chamfered and valso having a further portion of its advance face cut away to provide a checkingshoulder intersecting and extending at an angle to the chamfered portion of the tooth.

6. A circular thread-cuttingchaser having a plurality of peripherally-extending thread-cutting teeth/offsetting therefrom, including a front peripherally-extending `thread-cutting tooth; the said front tooth having its advance face chamfered and alsohaving a further portion of its advance face cut away to providea checking-shoulder located from` the trailing-face of the saidfront tooth a distance less than the root-thickness of the other of said thread-cutting teeth.

ALBERT F. BREITENSTEIN. 

